Insights into compositional changes of dissolved organic matter during a full-scale vermicomposting of cow dung by combined spectroscopic and electrochemical techniques

[Display omitted] •Vermicomposting can accelerate the humification process.•Vermicomposting led to higher changes in DOM composition and humification degree.•The two techniques were used as humification indices during vermicomposting.•The compositional changes of DOM were represented by the two techniques. Various spectroscopic and electrochemical techniques combined was used to investigate the compositional changes of dissolved organic matter (DOM) and the difference in humification degree during full-scale cow dung vermicomposting. This study also investigated that whether the two techniques could be used as humification indices. The physicochemical characteristics of vermicompost were superior to those of the control, indicating that vermicomposting significantly accelerated the humification process, which was confirmed by spectroscopic and electrochemical analyses. Meanwhile, the changes of three components identified and electron transfer capacities in vermicomposting further revealed that vermicomposting resulted in significant compositional changes of DOM and higher humification degree. Partial least squares path modeling and redundancy analysis revealed that the two techniques could be used as humification indices for vermicomposting. These results of this study demonstrated that the combination of spectroscopy and electrochemistry was applicable to characterize the compositional changes of DOM and the humification degree of vermicomposting.